This invention relates generally to power supplies, and more particularly, to switching uninterruptible power supplies.
Continuous enerigization is a requirement of many types of electrical and electronic apparatus. Well known examples of continuous energization dependent apparatus include computers and medical equipment. Even extremely brief interruptions of power to such equipment can cause serious if not calamitous difficulties. To alleviate problems associated with power interruption, there have been developed various systems for producing emergency power in the event of the failure of a principle power source. Generally such systems are identified as either uninterruptible or standby power supplies.
Standby systems utilize battery operated auxiliary power supplies that function only when a principle power supply fails. Typically, a charging system is provided to maintain a full charge on the battery of the auxiliary supply. In response to the output of a sensor, the auxiliary supply is coupled to a load after a detected failure of a primary power source. Although standby supplies are relatively simple and low cost, the required switchover from primary to auxiliary supply often produces interruptions in the continuity of power flow. For many types of equipment such interruptions in continuity are unacceptable.
In uninterruptible supply systems, a load is supplied directly through an auxiliary supply which can comprise an inverter powered by a battery. A primary power supply constantly charges the battery through a rectifier that typically supplies power to the inverter for energizing the load. Upon a failure of the primary supply, power continues to flow from the battery into the inverter. Thus, no interruption of power is experienced by the load unless the failure of the primary supply extends beyond the charge life of the battery. Although prior uninterruptible power supplies perform reasonably well, they do exhibit certain deficiencies. For example, known uninterruptible supplies are relatively expensive in that the rectifier employed by the system must be large enough to supply all power needed by the load under all circumstances and additionally because the continuously functioning auxiliary supplies must exhibit high reliability and durability. Relatively low power transmission efficiency is still another drawback of many existing uninterruptible supplies.
The object of this invention, therefore, is to provide an improved uninterruptible power supply that is highly reliable, efficient and relatively inexpensive.